Upsilon Andromedae

(The Planet Project)

The circle shows the location of the class F star Upsilon Andromedae (in the constellation Andromeda). A system of four planets orbits the star.

THE PLANETS

*Planet 1 orbits in 4.62 days, has a mass at least 0.62 times that of Jupiter, and is 0.06 astronomical units from the star (8.9 million kilometers, 5.5 million miles, or 15 percent Mercury's distance from the Sun).

*Planet 2 orbits in 238 days, has a mass at least 1.8 times that of Jupiter, and is 0.86 astronomical units from the star (129 million kilometers, 80 million miles.

*Planet 3 orbits in 3.6 years, has a mass at least 10.2 times that of Jupiter, and is 2.55 astronomical units from the star (383 million kilometers, 236 million miles, or 1.67 times Mars's distance from the Sun). The orbits of planets 2 and 3 are moderately eccentric.

*Planet 4 orbits in 10.5 years, has a mass at least that of Jupiter, and like Jupiter is 5.2 astronomical units from its star.

THE STAR

Upsilon Andromedae is a fourth magnitude (magnitude 4.09) class F (F8) ordinary dwarf 44 light years away. Its temperature of 6210 Kelvin and luminosity 3.4 times that of the Sun suggest a mass 1.3 times solar and a radius 60 percent larger than the Sun. Like most stars with planets, Ups And is rich in metals, its iron content (relative to hydrogen) 1.34 times that of the Sun. A roughly twelfth magnitude red dwarf (class M4.5) companion orbits at a distance from Ups And proper of at least 750 astronomical units and must take at least 16,000 years to make a full circuit. From the skies in the planetary system, it would glow like Venus does to us, though with a reddish cast.

The circle at lower right shows 54 Piscium, which both planetary and brown dwarf companions.
Written by Jim Kaler. Return to The Planet Project or go to STARS.